Reader response: Olfaction and risk of dementia in a biracial cohort of older adults
Bibliographic record
Abstract
We read with great interest the article by Yaffe et al.1 in which a strong association between poorer olfaction and incident dementia was reported. Exposure to airborne lead pollution decades earlier may play a role in this association. In older adults, higher cumulative lifetime exposure to lead, a well-established neurotoxin, was associated with impaired memory and accelerated declines in cognition,2–4 as well as smaller total brain volume, smaller volume of frontal and total gray matter, and more prevalent and serious white matter lesions.4 In primate studies, early life exposure to lead was associated with a greater burden of both β-amyloid plaques and neurofibrillary tangles in later life.2,3 Among older humans, the primary exposure pathway for lead was through inhalation of airborne lead pollution from leaded gasoline; mean blood lead levels declined 78% between 1976 and 1991 with the phase out of leaded gasoline.2 Cumulative lifetime lead exposure is associated with markedly worse olfactory function, and there is a negative dose–response relationship between exposure to vehicle exhaust and olfaction.5 A recent review suggested, “Inhaled Pb is likely able to directly reach olfactory tissues and translocate to the brain, given its strong deleterious neurocognitive effects.”5
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.021 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.002 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.022 | 0.016 |
| Insufficient payload (model declined to judge) | 0.010 | 0.011 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".